Inconsistent Flickr Photo Results

We’re trying to use Slickr Flickr on our website kwphotoclub.com. We are trying to show some our our photo group’s images the Flickr account https://www.flickr.com/groups/kwphotoclub/. It works to capture most our group’s images, but is not consistent. I regularly does not pick up new images. I’ve tried clearing cache numerous times. I’ve gotten it to work by downloading and then reloading the missing images, but that’s not even consistent. Is there some reason some images fail to come through the feed? Is there something about image size, resolution, etc?

Flickr Rest API with 30 photos

Group Photos On Flickr Photostream

https://www.flickr.com/groups/kwphotoclub/

Group Photostream

Differences In Results

The Flickr RSS feed shows the latest photo but the FLickr API does not unless you ask for at least 30 photos. This suggests that it something to do with caching on Flickr. Why should asking for 30 photos instead of 12 photos cause to give you a different set of recent photos unless the query is being directed to a different server?